Found in the Catacombs of Carthus.
From the Catacombs of Carthus bonfire, turn left and go downstairs. Climb up any of the two sets of stairs found on the nearby wall (one of them hidden behind an illusory wall). The ashes are on a corpse lying at the far end of this area, guarded by three Skeleton Swordsmen.
Extends the Shrine Handmaid's inventory to include the following items:
|∞||Yellow Bug Pellet||1,500|